David Moyes saw his Manchester United campaign start in perhaps the best possible way, as Robin van Persie terrorised Swansea to deliver an emphatic away win for the reigning Premier League champions.

Van Persie scored two fine individual efforts to swing the game decisively in United's favour, with strike partner Danny Welbeck also bagging a brace at the Liberty Stadium.

There was also a 30-minute cameo from Wayne Rooney, whose body language perhaps left something to be desired, but nevertheless provided a clever assist for Welbeck's second.

Swansea's own early substitute, £12 million summer signing Wilfried Bony, grabbed the home side's consolation.

After the match, Van Persie expressed his delight at the opening win—having been held to a 1-1 draw at the same venue last season.

"We are very happy," Van Persie told Sky Sports. "To play against Swansea, first game of the league, away from home, it is tough.

"You could see at times that they are a great team, I love the way they play. It’s a big win."

In truth, it was not a win that had looked likely after the opening half hour. Swansea—despite leaving Bony on the bench after being involved at international level in midweek—looked threatening, whereas Moyes' United side, featuring a four-man midfield with Ryan Giggs on the left, lacked a little invention.

Phil Jones was denied by Michel Vorm in United's best early chance, while Wayne Routledge saw his low effort turned away by David de Gea. But then came Van Persie's intervention: last year's league top scorer taking on Giggs' lofted through ball before volleying past Vorm acrobatically.

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Wayne Rooney played 30 minutes.

It was an exquisite strike that stunned the Swans, and two minutes later they were two down. It was Welbeck with the finish, as he arrived in the right place to turn home Antonio Valencia's low cross.

Swansea manager Michael Laudrup reacted at half-time by bringing on both Bony and Pablo Hernandez, but it was Van Persie who would get the game's decisive third goal.

The former Arsenal man would later describe the strike as like "going back to the streets"; using his close control (and the distracting runs of Rooney, brought on moments earlier, and Welbeck) to shift the ball onto his left on the edge of the box before rifling home.

The points seemed to be in the bag at that point, even as Bony opened his Premier League account with 10 minutes remaining. The forward, who showed his raw power throughout his display, showed good poise and a decent eye for goal to slip home after being played in by Hernandez.

The game was all but over, but the finishing was not. Rooney had looked somewhat disinterested at points in the second half (getting needlessly caught offside on more than one occasion) but sprung into life in injury time, slipping through Welbeck. The England man still had a lot to do, but calmly lobbed the onrushing Vorm to cement a key win for Moyes.

"Yeah, it’s a dream start," Moyes said. "As Manchester United manager your job is to win your games, and the players did that today.

"They are very well managed under Michael Laudrup but we limited their opportunities. We scored a little bit against the run of play, but Robin scored a great goal for us. I’m more than happy to win 4-1."

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Manchester United took the points.

Key Player Grades

Robin van Persie: A

New season, same execution. The Dutchman was by no means perfect in his all-around play, but his two strikes came almost out of nothing and secured a comprehensive win for the home side. There is no better striker in the league than RVP, and he proved that again on the very first day of the season.

Wayne Rooney: C

In his 30 minutes on the pitch, the unsettled striker did some good things—linking play well, providing an assist for Welbeck—and some bad, showing a somewhat lax attitude towards certain basic duties on too many occasions.

But his appearance nevertheless shows a certain reintegration into Moyes' thoughts, suggesting perhaps he might stay at Old Trafford beyond the end of the transfer window.

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Wilfried Bony looked solid.

Wilfried Bony: B+

From his performance after coming on as a half-time change, it looks like £12m is a fair deal for the powerful forward. Bony caused Nemanja Vidic and Rio Ferdinand consistent problems with his movement and stature, but then showed great technique with the ball on the floor to grab Swansea's only goal.

Perhaps most encouragingly for Laudrup, he showed a good understanding with strike partner Michu—the pair being unselfish as they looked to feed each other. Today's result was disappointing, but the signs remain encouraging for the Welsh club.

What's Next?

Manchester United will now turn their attentions towards next Monday's blockbuster home game against Chelsea, a first real measure of the title credentials of both sides.

Swansea, meanwhile, have a day less to prepare for an away trip to White Hart Lane, where Andre Villas-Boas' Spurs will be hoping to inflict a second successive defeat.